1. Field of the Invention
This invention relates to improved impact absorbing compressible composites. These composites can be shaped into smooth compound curves and find application wherever high efficiency impact absorption is called for such as in athletic wear, in seating systems, in vehicle interior padding materials and the like.
2. Background Information
There is a well-recognized need for high performance materials for spreading or absorbing impacts. In recent years, athletes, athletic equipment manufacturers and sports medicine professionals have recognized the need for improved impact absorbing materials in athletic equipment. These materials find application as heel pads and foot sole pads in shoes to absorb the shock of foot strike and as cushioning points under football or hockey pads such as shoulder pads, thigh pads, hip pads and the like to name but a few typical applications. Similar needs may be found in seating systems and in vehicle interiors, to name but a few representative fields in which impact absorption is a major interest.
One common approach to impact absorption in the past has involved using felts or blocks of a soft padding material. Padding materials known heretofore include cotton padding, horsehair padding, foam rubber, foamed plastics, sponge rubber and the like. In these designs, the inherent resilience of the padding material is employed to absorb and disperse the applied impact. These designs have the disadvantage that they often "bottom out" or fully compress on severe impacts of the type regularly encountered during use such as in athletic equipment or in vehicle interiors and thus provide minimal protection. When made thicker to avoid this problem, they become cumbersome and can interfere with the design of the article being padded, and in the case of athletic equipment can interfere with the wearer's freedom and performance.
Impact absorbers have also been proposed which employ fluid-filled bladders such as cushioning air sacks These devices rely upon the compressibility of the enclosed fluid to provide the desired shock absorbing. In some embodiments of these devices, the fluid is fully enclosed and can not escape. In others, the fluid is gradually and controllably forced out of the bladder during the impact with the rate of release being selected to prevent exhaustion of the fluid during the impact event. While effective as shock absorbers, these devices can have the failing of ballooning or otherwise expanding in one region when another region is being compressed. This can lead to discomfort or at minimum give an unnatural or unstable feel to the user. In the case of footwear, this problem can lead to an unstable foot plant with increased opportunity for injury. Another issue with this type of pad has related to problems in forming shapes based on compound curve and to retaining structural integrity with the above-described ballooning.
Representative patents in the field of shock absorbing or impact absorbing devices include U.S. Pat. No. 4,513,449, SHOCK ABSORBING ATHLETIC EQUIPMENT; U.S. Pat. No. 4,370,754, VARIABLE PRESSURE PAD; U.S. Pat. No. 4,453,271, PROTECTIVE GARMENT; U.S. Pat. No. 4,217,705, SELFCONTAINED FLUID PRESSURE FOOT SUPPORT DEVICE, all issued to Donzis, U.S. Pat. No. 4,446,634 for FOOTWEAR HAVING IMPROVED SHOCK ABSORPTION; U.S. Pat. No. 4,397,104 for INFLATABLE SOLE-SHOE; U.S. Pat. No. 2,863,230 for CUSHIONED SOLE AND HEEL FOR SHOES; U.S. Pat. No. 4,229,889 for PRESSURIZED POROUS MATERIAL CUSHION SHOE BASE; U.S. Pat. No. 4,637,716 for METHOD FOR MAKING ELASTOMERIC SHOE SOLES; U.S. Pat. No. 4,635,384 for FOOTWEAR SOLE; U.S. Pat. No. 4,610,099 for SHOCK-ABSORBING SHOE CONSTRUCTION; and U.S. Pat. No. 4,571,853 for SHOE INSERT.
It is an object of the present invention to provide an improved impact absorbing composite. It is desired that this composite provide superior shock absorbing performance and also be capable of being formed into complex compound curve shapes, be durable and hygienic.